One of the key differences between the iPhone 4 and iPhone 4S is the availability of Siri on the newer smartphone. There have been a few hacks and allegedly legal options that put Siri on older versions of the iPhone, but nothing officially sanctioned by Apple.

The latest Siri workaround comes from iOS hackers Grant Paul, known as chpwn, and Ryan Petrich. In a recent blog post, the duo unveiled Spire, which is a "new tool for installing Siri on previously unsupported, but jailbroken, devices," Paul said. As you might recall, an iOS 5 jailbreak was just released.

The 100MB download is available via Cydia and it will add Siri to any device running iOS 5.

If that sounds a bit too good to be true, though, it is. Actually getting Siri to work on a device other than the iPhone 4S will require some technical know-how.